The invention relates to a compressed-air supply device for a utility vehicle, with a valve housing and with an exchangeable air drier cartridge. The air drier cartridge having a filter device which purifies air flowing out of the valve housing into the air drier cartridge. The filter device separates a pre-filter region facing the valve housing from a post-filter region which faces the air drier cartridge and in which foreign particles picked up by the filter device are collected. Parallel to the filter device, a non-return valve is provided, which prevents an air flow from the pre-filter region into the post-filter region and allows an air flow from the post-filter region into the pre-filter region.
The invention relates, furthermore, to a valve housing for a compressed-air supply device with an exchangeable air drier cartridge. The air drier cartridge has a filter device which purifies air flowing out of the valve housing into the air drier cartridge. The filter device separates a pre-filter region facing the valve housing from a post-filter region which faces the air drier cartridge and in which foreign particles picked up by the filter device are collected. Parallel to the filter device, a non-return valve is provided, which prevents an air flow from the pre-filter region to the post-filter region and allows an air flow from the post-filter region into the pre-filter region.
Such compressed-air supply devices with a valve housing and with an air drier cartridge are used in order to supply compressed-air consumers of a utility vehicle with dry and purified air. What may be considered as compressed-air consumers are, for example, the brake system or a pneumatic spring installation. The drying of the air in this case takes place by means of a desiccant present mostly as a granulate. Moreover, it is useful to remove foreign substances, for example compressor oil, from the compressed air.
This oil is supplied to the compressed-air supply device, together with the air, in a partially vaporous state of aggregation, and, because of the high temperatures and high pressures, it is in multiple cracked form. The substances therefore present are harmful to the components of a compressed-air installation. For example, cracked oils seriously lower the service life of sealing elements.
One example of a compressed-air supply device in which these foreign substances are removed from the compressed air supplied is disclosed in DE 103 29 401 A1. Here, a coalescence filter is provided, which purifies the compressed air flowing into the filter cartridge, the foreign particles extracted from the air accumulating in a post-filter region. So as to be able to empty the post-filter region from time to time, a non-return valve is provided parallel to the coalescence filter. This non-return valve makes it possible, by a discharge valve in the valve housing being opened, for the foreign particles to flow out and to be ejected into the atmosphere.
The non-return valve therefore comes into intensive contact with the collected foreign particles, thus making it necessary to manufacture the non-return valve from comparatively costly materials. This would be manageable per se in light of the overall costs of a compressed-air supply device. The problem, however, is that the air drier cartridge has to be exchanged from time to time. Consequently, the production of the non-return valve from costly material is not only reflected in the procurement costs of the compressed-air supply device, but especially also in the costs of the exchangeable drier cartridge. In terms of the overall costs of the air drier cartridge, however, the costs of the non-return valve constitute an appreciable proportion.
The object on which the invention is based is to make available a compressed-air supply device, so that the costs associated with the exchange of the air drier cartridge are reduced.
The invention builds on the generic compressed-air supply device in that the non-return valve is arranged in the valve housing. The non-return valve is thus preserved even in the event of a cartridge change. It therefore does not contribute to the costs incurred when the filter cartridge is exchanged.
Expediently, there is provision for the post-filter region to have a collecting duct for the foreign particles picked up by the filter device, at least one portion of the collecting duct defining a horizontal plane when the compressed-air supply device is in the installed uninclined state, and for the non-return valve to lie below the plane. This ensures that, at least when the utility vehicle is standing horizontally, a complete emptying of the collecting duct via the non-return valve can take place.
It is especially useful in this respect that, in the event of an inclination of the compressed-air supply device of up to 15 degrees with respect to the horizontal plane about any axis, the non-return valve lies on a lower vertical coordinate than the lowest point of the at least one portion, defining the horizontal plane, of the collecting duct. The collecting duct is thus emptied even when the utility vehicle is in an oblique position, for example when traveling up or down a hill.
The invention is developed in a particularly useful way in that the air drier cartridge has a cartridge housing receiving a desiccant box, and in that the cartridge housing is connected to the valve housing directly via a seal. Such compressed-air supply devices are also designated as open systems. In particular, the air drier cartridge is not equipped with a foot flange, via which closed systems are connected to the valve housing.
The invention is especially suitable for open systems, since a scavenging duct for transferring the foreign substances which have accumulated in the collecting duct of the drier cartridge into the valve housing can be implemented without any obstruction, that is to say, in particular, without a bypass or drilling through of a foot flange.
The invention builds on the generic valve housing in that the non-return valve is arranged in the valve housing.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.